Adding missing documentation about the purpose of Devcontainers's support

.devcontainer/README.md

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+# Devcontainers support for Quarkus
+
+## Motivation
+
+Sometimes, you don´t have the right dev environment to explore and contribute in the `Quarkus`project. With this idea in Mind, `Devcontainers` was added to use the capabilities from Cloud Environments like `Github Codespaces`.
+
+**Note:** Not use in local DevContainer with Quarkus because it is massive and you are adding another abstraction layer.
+
+## Getting Started
+
+If you visit the project in Github: https://github.com/jabrena/quarkus in the main view, exist a Green button named `Code` if you click in the dropdown, you will see the option `Codespaces` so, if you click in the button `Open in Codespaces`, you will open a new Tab in your web browser to load Quarkus in Codespaces.
+
+## Benefits
+
+Quarkus project has plenty extensions, if you are interesting to review any extension, you could use DevContainers to review in an easy & quick way.
+
+**Examples:**
+
+```bash
+#High performance Data Structures
+./mvnw clean verify -pl extensions/agroal -am
+
+#Dependency Injection Engine in Quarkus
+./mvnw clean verify  -pl extensions/arc -am
+
+#Devservices
+./mvnw clean verify  -pl extensions/devservices -am
+
+#Panache
+./mvnw clean verify  -pl extensions/panache -am
+```
+
+Enjoy!
+
+## References
+
+- https://containers.dev/
+- https://github.com/features/codespaces
+- https://github.com/codespaces